Diagnosis
The M2 doesn't have a way to just edit the Wi-Fi credentials in settings. It's designed to connect once during setup, so changing networks requires a full reset and re-setup process.
How to Fix It
You have to factory reset the hub first. Unplug it, then press and hold the pinhole reset button on the bottom. While still holding the button, plug the power back in. Keep holding for another 5-10 seconds until you see the status light flash yellow rapidly, then release. The hub is now reset. Then, set it up fresh in the Aqara app as if it were new, using your new Wi-Fi network name and password when prompted.
If That Didn't Work
If your new router has a different security protocol (like WPA3) or is using a hidden SSID (network name), the Aqara hub might not support it. The M2 supports WPA/WPA2 Personal with a visible SSID. It does not support WPA3-only mode or enterprise networks. You may need to adjust your router's settings temporarily for the setup.
Heads Up
Remember, this factory reset means you lose all your connected Zigbee devices and automations. You'll need to physically go to each sensor and re-add them to the hub one by one after this process. There's no cloud backup for your device network.